Method and device for stabilizing high-speed unwinding of a strip product

ABSTRACT

The invention relates to a method and a device for stabilising high speed running along a longitudinal direction, of a band ( 4 ) applied on a rotary surface ( 3 ) and along which a portion of the surrounding air forms a boundary layer ( 43 ) trapped with the band ( 4 ).  
     According to the invention, a deflecting member ( 5 ) is placed in the dihedron (G) between the band ( 4 ) and the rotary surface ( 3 ). Said deflecting member ( 5 ) has a face ( 50 ) directed toward the band which is tilted with respect thereto and is fitted with at least one orifice ( 55 ) emerging into an inner space ( 51 ) provided inside said deflecting member ( 5 ) and connected to an outer zone. Thus, said tilted face ( 50 ) forms, with the inner face ( 41 ) of the band ( 4 ), a convergent (C 1 ) wherein the pressure increases with respect to the pressure in the inner space ( 51 ) and the differential pressure determines the exhaust of a certain air flow rate through the orifice ( 55 ) and the separation of the remaining portion of the air mass trapped in the boundary layer ( 43 ).

[0001] The invention relates to a method and a device enabling tostabilise and to guide a band-type product running at high speed along alongitudinal direction, in particular in a cold rolling mill for metalbands, more especially thin sheets of aluminium.

[0002] A cold rolling mill of a metal band-type product comprises,generally speaking, one or several roll stands each including twoworking rolls resting on back-up rolls and associated with means forcontrolling the running of the band between the working rolls.Generally, the band unfolds from a spool placed on a side upstream ofthe roll stand(s) and winds on a coiler placed on the downstream side.The installation comprises on the other hand numerous appended memberssuch as means for inserting the band into the roll stands, means foradjusting rotary speeds of the different members and a number ofdeflecting rolls which may have an adjustable position and whereon theband is applied in order to be guided along a determined path.

[0003] Taking productivity, production and profitability criteria intoaccount, a rolling mill of very thin sheets, in particular of aluminium,includes, generally, a single rolling stand operating from spool tospool, between an unwinder and a winder.

[0004] Conventionally, a roll stand comprises two standards spacedapart, between which are installed a set of rolls, for example, in thecase of a quarto roll stand, two working rolls associated respectivelyto two back-up rolls. Each roll is rotatably mounted, at its ends, onbearings carried by chocks slidingly mounted between the stanchions ofthe standards of the roll stand and clamping means resting on the chocksof the back-up rolls enable to realise the reduced thickness requestedon the rolled band.

[0005] A very thin thickness may be thus obtained and, for example, inthe case of aluminium sheets, the thickness may range from 3 to 300micrometers. The items of equipment of the installation must, obviously,be adapted to so thin thicknesses, in particular for winding the spool.

[0006] For exemplification purposes, FIG. 1 represents schematically arolling mill of an aluminium sheet including a roll stand A placedbetween an unwinder D carrying a spool B₁ and a winder E whereon isformed a spool B₂ after passing the product M between the working rollsof the rolling stand A.

[0007] On its path between the unwinder and the winder, the band M isguided by a number of deflecting rolls D. In particular, a roll D₁ formeasuring the flatness is placed downstream of the roll stand A in orderto detect the possible defects to be corrected by acting on means foradjusting the rolling conditions. Moreover, a wrapping roll D₂, ofadjustable level, enables to adjust the angle for winding the band onthe flatness roll D₁. This roll D₂ may be moved upwards for easierengagement of the band on the winder E.

[0008] Obviously, the installation of FIG. 1 is represented only forexemplification purposes, whereas other types of installation may beused. For example, a tandem rolling may be provided in a mill includingseveral stands placed successively on the path of the band to realisegradual reduced thickness or still reversible rolling performedalternately in both directions, the mill being associated with twocoilers which operate alternately as an unwinder and as a winder. On theother hand, the rolled band may undergo a number of treatments, eitherupstream, or downstream of the rolling process and, in more recentinstallations, these various treatments should be performed on acontinuous line.

[0009] However, for rolling thin sheets of aluminium, the smallthickness of the metal band rolled causes particular operation of theinstallation since the length of a spool may be several tens ofthousands of metres and the duration of a rolling pass may thereforereach several hours. Under these conditions, it is impossible to realisea reversible rolling process.

[0010] On the other hand, there is no point, as for other installations,in realising continuous assemblies since the ratio between the durationof the rolling process and the replacement duration of the spools isvery high.

[0011] In practice, the single parameter whereon may be actedefficiently to increase the productivity is the speed of the rollingprocess and it has been sought therefore to improve the performances ofthe installations. In particular, for rolling thin sheets of aluminium,very high rolling speeds may be now realised, for example of the orderof 2000 metres per minute, speeds of 3000 metres per minute being evencontemplated.

[0012] However, at very high speeds, it becomes very difficult to ensurestability of the guiding of the band which has a tendency to float onthe deflecting rolls, in particular the wrapping roll, which may lead todefects in the spool during the winding process. It is thereforenecessary, in installations operating at very high speed, to detectimmediately a possible guiding defect in order to bring the speed downto a level enabling to restore stable running.

[0013] But other shortcomings appear, for winding a metal band into aspool, at high speed.

[0014] It is known, indeed, that in order to be wound into contiguousspires, the band should be held under traction by the winder E. However,the traction which may be applied to a sheet of aluminium is small and,even with a usual specific traction of the order of 3 to 5 kg/mm², thetraction load which ensures the application of the band on the spoolwound may only be a few tens of kg and does not exceed, in practice, 200kg.

[0015] Still, it has been observed that, at high speed, such traction istoo small to ensure good application of the spires on one another andthere results increased global diameter of the spool.

[0016] This phenomenon, called volume swell, biases the usualcalculations of band length and of spool diameter.

[0017] To remedy this shortcoming, it has been suggested to fit thecoiler with an additional roll, so-called finishing roll, which isinstalled on a hinged arm and rests, from the outside, on the bandduring the winding process.

[0018] However, it is not desirable to increase the number of rolls ordevices in contact with the band since there results a risk of markingthe product.

[0019] The object of the invention is to remedy such shortcomings thanksto a method and a device enabling to ensure stable running and windingof the band, even at very high rolling speeds and, thus, to increaseconsiderably the productivity of an installation without notablemodification thereof.

[0020] To solve this problem, the applicant company has studied indetail the running conditions of a band at high speed, in particular forrolling a thin sheet of aluminium and it has appeared that thedifficulties met for guiding the band, the flatness measurement and thewinding into a spool after the rolling process, might all be explainedin that from a certain running speed, a portion of the air situatedclose to the band, might be trapped therewith, abutting on the obstaclesplaced on the path of the band such as the guiding rolls or the workingrolls.

[0021] For working rolls which are driven into rotation and whereof theclamping determines the reduced thickness, such trapping of air isunimportant.

[0022] However, in the case of a deflecting roll whereon the band issimply applied under traction, the air trapped with the band causes,upstream of the application zone, a dynamic pressure which, by a wedgingeffect, is capable of lifting the band slightly. This is even moresensitive as when rolling thin sheets of aluminium since, as seen above,the traction load which determines the application of the band on theroll, is necessarily limited.

[0023] There forms then, between the sheet and the roll, an air cushionwhich, in the case of a deflecting roll or a wrapping roll, may disturbthe guiding of the band, the latter being slightly lifted and liabletherefore to move laterally.

[0024] Such an air cushion formation phenomenon by air trapping betweena band running at high speed and a deflecting roll or a spool hadalready been observed in the paper industry.

[0025] To avoid this shortcoming, it has been suggested, in the documentDE-A-19839916, to place in the dihedron formed upstream of the line ofcontact, a flexible blade which enters the interval between the innerface of the band and the spool and brakes the air stream, the pressureupstream of the line of contact being thus diminished.

[0026] It has also been observed, in the case of a cool-down roll for anoffset printing machine, that the paper band may drive a certain amountof air which might enter between the band and the roll, the air cushionthus formed constituting an insulating layer which reduces the cool-downeffect.

[0027] To avoid this shortcoming, it has been suggested, in the documentEP-A-0812695, to place in the upstream dihedron between the band and theroll a suction device in the form of a hollow caisson connected to asuction fan and having a flat face and a curved face, respectivelyparallel to the band and to the roll, which converge to a narrowed endalong which is provided a slot which emerges therefore between the bandand the roll, close to the line of contact. The air situated in thisportion is therefore sucked in by this slot and the pressure upstream ofthe line of contact is diminished, the band being thus held applied onthe roll, without any risk of being lifted.

[0028] As it has been noted that the various shortcomings mentionedabove in the case of the metal band rolling at very high speed resultfrom the air trapping effect with the band, it has been suggested thatthe devices provided previously, in the paper industry, to avoid thisshortcoming, might advantageously be used for metal band rolling at highspeed.

[0029] It has appeared, however, that the devices known previously andeither simply braking, or sucking in the air trapped, would not beefficient enough or even harmless, in the case of a metal sheet, inparticular of aluminium.

[0030] Indeed, as indicated above, because of the very thin thickness ofthe aluminium sheets, the traction load which may be applied isrelatively small and a suction nozzle placed close to the line ofcontact between the band and the spool might deflect the band which,when resting against the suction member, might be damaged or even torn.

[0031] Detailed studies have therefore related to the aerodynamicconditions of air circulation to develop a device which, withoutrequiring air suction liable to deflect the band, causes stratifiedphenomenon acting only on the boundary layer of air trapped with theband.

[0032] The invention relates therefore generally speaking, to a methodand a device for stabilising high speed running, along a longitudinaldirection of a band being applied from a line of contact, over at leastone angular sector of a rotary revolution surface around an axiscrosswise to the running direction, and connecting tangentially to therotary surface while forming, on the upstream side in the runningdirection, a dihedron delineated, on one side by an outer face of therotary surface and on the other side, by an inner face of the band alongwhich a portion of the surrounding air forms a boundary layer trappedwith the band toward the line of contact, a deflecting member beingplaced in the dihedron in order to modify the conditions of circulationof the air trapped with the band, said deflecting member having a firstface directed toward the inner face of the band and a second facedirected toward the outer face of the rotary surface.

[0033] According to the invention, at least the first face of thedeflecting member is tilted toward the inner face of the band, in therunning direction thereof and is fitted with at least one orificeemerging into an inner space provided inside the deflecting member andconnected to an outer zone, said tilted face forming, with the innerface of the band, a convergent wherein the pressure increases withrespect to the pressure in the inner space), the differential pressuredetermining the exhaust, through the orifice of the tilted face and theinner space, of a certain air flow rate and the separation of theremaining portion of the air mass constituting the boundary layertrapped with the band.

[0034] Particularly advantageously, the inner space of the deflectingmember is not connected to a suction fan, but simply to an outer zonesituated at atmospheric pressure, the circulation of the air takingplace thus naturally, without true suction, at the deflecting member.

[0035] Preferably, the second face of the deflecting member, directedtoward the rotary surface, is tilted with respect thereto, in order toform a convergent determining an increase in pressure of the air trappedwith the rotary surface, whereof a portion is evacuated toward the outerzone connected to the inner space passing through at least one orificeprovided in said second face.

[0036] Such a stabilisation device according to the invention may beapplied either to a deflecting roll with a cylindrical profiledetermining a change in direction of the running plane of the band, orto winding the band into a spool in order to prevent the trapping of airbetween the superimposed spires.

[0037] For winding into a spool, the deflecting member of the airconsists of a hollow profile, installed on a supporting means adjustablerelative to the diameter of the spool, in order to maintain thedeflecting member in optimum position with respect to the inner face ofthe band, as the latter is wound gradually into a spool.

[0038] Preferably, this supporting arm of the deflecting member of theair exhibits a variable length and is rotatably mounted around an axisparallel to the axis of the spool, said arm being associated with meansfor adjusting its orientation and its length relative to the diameter ofthe spool, to position the profiled member inside the upstream dihedron.

[0039] Advantageously, the adjustable supporting means of the deflectingmember is installed on a wrapper associated with the spool for easierbeginning of the band winding process, the supporting means being foldedin the jig of the wrapper when the latter is at the beginning of thewinding position and unfolded after winding a few spires and moving thewrapper away, in order to place the deflecting member close to the lineof contact, at the end of the upstream dihedron.

[0040] The invention also relates to the use, in a rolling mill formetal bands, in particular of aluminium, of such a stabilisation devicewhich may be placed upstream of at least one deflecting roll, in orderto direct application of the band on the roll without interposition of aair layer. This deflecting roll may advantageously be a flatnessmeasuring roll, the device then enabling not to disturb the measuringprocess by trapping air between the band and the roll.

[0041] But the invention may also be used advantageously for winding therolled band on a coiler placed at the end of the line, the stabilisationdevice being then placed upstream of the line of contact with the spoolalready wound in order to avoid any volume caused by the air trappedbetween the spires and to ensure guiding stability of the band duringthe winding process.

[0042] Other advantageous characteristics are mentioned in the claims.

[0043] But the invention will be understood better by the followingdescription of certain embodiments given for exemplification purposesand represented on the appended drawings.

[0044]FIG. 1 is a diagrammatical view of a thin sheet rolling mill.

[0045]FIG. 2 is a cross-sectional view, at enlarged scale, of adeflecting member of the air according to the invention, applied to thewinding of a spool.

[0046]FIG. 3 shows, in elevation, the whole device fitted on a winderplaced at the outlet of a mill.

[0047] As indicated above, FIG. 1 shows, schematically, the wholerolling mill of a sheet of aluminium which unfolds from a spool B₁ andis re-wound, at the outlet of the mill A to form a new spool B₂. Theband M is guided by a plurality of deflecting rolls which ensure stablerunning, in particular, a roll for measuring the flatness D₁ and awrapping roll D₂.

[0048] Moreover, a loop yarn twister D₃ composed of two fixed rollssurrounding a central roll of adjustable level, enables to adjust thetension upstream of the mill A.

[0049] The mill A represented schematically on FIG. 1 and more in detailon FIG. 3, may be, for example, of quarto type including two workingrolls 1, 1′ resting, respectively, on back-up rolls 11, 11′ and eachrevolving round a shaft carried, at its ends, by chocks, respectively12, 12′, 13, 13′ which are slidingly mounted along vertical guidingfaces 14 provided on two fixed standards 10 constituting the roll standof the mill.

[0050] Downstream of the mill, the band passes successively over a roll15 for measuring the flatness and on a wrapping roll 16 which isslidingly mounted on both standards 10 of the roll stand and whereof theposition may be adjusted by a jack 17 relative to the nature of themetal and to the thickness of the band, in order to adjust the angle ofapplication on the flatness roll 15.

[0051] The winder E whereon is formed the rolled spool B₂ comprises,conventionally, an extensible mandrel 2 mounted cantilever on a chassis21 and driven into rotation round its axis 20. In a well-known fashion,as shown on FIGS. 1 and 3, the winder E is associated with a wrapper Finstalled on a chassis 22 hinged on the standards 10 of the mill aroundan axis 23 parallel to the running plane of the band M and which mayrevolve, under the action of a means not represented, between a liftedposition and a position spaced apart. The wrapper F comprises an openportion 24 which, in the lifted position of the chassis 22, engages onthe mandrel 2 of the winder E.

[0052] At the beginning of the rolling process, the wrapping roll 16 israised by the jack 17 in a position spaced apart 16′ letting through thehead M₁ of the band M and its engagement on the mandrel 2. Known means,provided in the open portion 24 of the wrapper F and not represented onthe Figure, pick up the head of the band for easier beginning of thewinding process into superimposed spires. When the number of spires issufficient to support the traction of the band, the wrapper F is movedaway by the jack 24 to adopt the position represented on FIG. 3.

[0053] A spool 3 is thus formed on the mandrel 2, whereof the diameterincreases gradually, as indicated on FIG. 3.

[0054] The band M connects therefore tangentially to the spool 3, alonga line of contact 30 parallel to the axis 20 of the mandrel 2, whileforming a dihedral angle G with the outer face 31 of the spool 3,directed upstream with respect to the running direction.

[0055] It is known that high speed displacement, parallel to itself, ofa thin surface in a fluid causes, by friction, trapping of the moleculesof the fluid, for example the surrounding air, situated in closevicinity of the band in motion.

[0056]FIG. 2, for example, shows with an enlarged scale the zone forwinding the band M on the spool 3, and represents, on the right-handside, the variation diagram of the speed vector (U) of the air which,from a distance (e) from the inner face 41 of the band 4 goes from azero value to the value (V) of the running speed of the band 4, whileremaining parallel to itself. There exists therefore, along the innerface 41 of the band 4 directed toward the spool 3, a thickness of air inmotion 43 called boundary layer wherein a stratified flow takes place ata speed which increases gradually, while getting closer to the band 4,to reach the speed thereof along its inner face 41. The same goes alongthe outer face 42 of the band.

[0057] This boundary layer 43 accompanies the band 4 in its runningdirection and abuts against the spool 3 whereof the outer face 31directed upstream, i.e. facing the running direction, forms, with theinner face 41 of the band 4, a dihedron G which converge toward a lineof contact 30 of the band 4 with the last spire wound 32.

[0058] This blocking, upstream of the line of contact 30, of the airtrapped along the face 41 of the band determines an increase in pressurewhich may cause slight lifting of the band 4 and the introduction of afine air layer between the inner face 41 of the band 4 and the spool 3.

[0059] The idea of the invention consists in providing aerodynamicconditions of air circulation in the upstream dihedron G enabling toseparate the boundary layer 43 upstream of the line of contact 30.

[0060] This separation of the boundary layer 43 is performed byevacuating toward the outside a portion of the air flow rate trappedwith the band, by means of a deflecting member 5 placed in the upstreamdihedron G and extending between the inner face 41 of the band and theouter face 31 of the spool, parallel to the line of contact 30. Thisdeflecting member 5 consists of a hollow profile having at least oneface 50 directed toward the inner face 41 of the band 4 and tilted withrespect thereto, in the running direction, in order to form a convergentC₁ whereof the section diminishes gradually by causing an increase inpressure of the air trapped with the band in the boundary layer 43.

[0061] This tilted face 50 is fitted with a plurality of orifices in theform of slots 55 which emerge in the inner space 51 provided inside thehollow profile 5. The latter is closed at its ends and fitted with anorifice linked by a conduit 53 to an outer zone 54 located, for example,at atmospheric pressure.

[0062] The increase, by a wedging effect, in pressure in the convergentC₁ determines therefore the passageway through the slots 55 for aportion of the air trapped in the boundary layer 43 which escapesthrough the conduit 53 toward the zone at smaller pressure 54. The flowrate of air trapped toward the line of contact 30 diminishes and theboundary layer 43 thus comes loose from the inner face 41 of the band 4to be attached to the tilted face 50 of the deflecting member 5 whileforming a stream of stratified flow which escapes through the slot 55and the conduit 53.

[0063] The pressure of the trapped air increases only up to thedownstream end of the deflecting member 5 and then decreases. Thepressure being smaller upstream of the line of contact 30, the airshould not enter between the last spire 32 of the spool 3 and the spire33 being formed.

[0064] In the preferred embodiment represented on FIG. 2, the secondface 50′ of the deflecting member 5 directed toward the winding surface3 is also tilted with respect thereto in order to form a secondconvergent C₂ which increases gradually the pressure of the air trappedby the rotation of the spool 3. This second tilted face 50′ is alsofitted with a slot 55′ which emerges in the inner space 51 of the hollowprofile 5.

[0065] There is thus a natural circulation along both faces 50, 50′ ofthe hollow profile 5 which diminishes the pressure at the end of thedihedron G, upstream of the line of contact 30, without any air suctionat the end 52 of the deflecting member 5 which enters the dihedron Gbetween the inner face 41 of the band and the face 31 of the spool 3. Itshould be noted that it is needless to taper the end 52 of thedeflecting member 5 which must simply limit both convergents C₁, C₂ todetermine the stratified air flow along both tilted faces 50, 50′without extending toward the line of contact 30.

[0066] To determine such stratified flow, it is sufficient, normally,that the conduit 53 emerges simply in a calm zone where the air speed iszero and the pressure is equal at atmospheric pressure.

[0067] Indeed, the differential pressure between both convergents C₁, C₂and the outlet 54 of the exhaust conduit 53 determines natural aircirculation through the slots 55, 55′.

[0068] However, if the width of the band and, consequently, the lengthof the profile 5 as well as the length of the exhaust conduit 55 are toogreat and might cause high loss of pressure, taking the dynamicoverpressure into account due to the rotary speed of the spool, it maybe preferable to link the exhaust conduit 53 to a suction device.However, the aim of the latter is simply to compensate the loss ofpressure in the circuit and not to realise true air suction in the apexof the dihedron downstream of the deflecting member 5. The bandtherefore cannot be damaged by application thereof on the downstream end52 of the deflecting member 5, even in the case where the band issubjected to relatively small traction load.

[0069] The shape of the hollow profile 5, in particular the profile andthe tilting of the faces 50, 50′ and their optimum positioning withrespect to the band to be wound 4 and the line of contact 30 may bedetermined empirically or by calculation in order to obtain the effectsought, while studying the conditions of air circulation taking intoaccount the running speed v of the band 4, and losses of pressure in theprofile 5 and the exhaust circuit.

[0070] On the other hand, the diameter of the spool and, consequently,the position of the line of contact 30 and the orientation of the band 4varies obviously, during the winding process. The position of thedeflecting member 5 should be maintained permanently inside the dihedronG and, to do so, it is advantageous to use the device represented indetail on FIG. 3.

[0071] As indicated above, at the outlet of the mill, the rolled band Mpasses over two deflecting rolls, respectively, a flatness measuringroll 15, placed at the gap between the working rolls 1, 1′ and awrapping roll 16 which is slidingly mounted along guiding rails providedon the standards 10 of the mill and whereof the level may be adjusted bymeans of a jack 17 relative to the thickness and to the nature of therolled band, the wrapping roll 16 being raised in high position 16′ atthe beginning of the rolling process for easier passage of the head ofthe band M and its engagement on the mandrel 2 of the winder E. On theother hand, the latter is associated with a wrapper F installed on achassis 22 which may revolve round an axis 23 between a raised position,represented on FIG. 1, for which the wrapper is engaged on the mandrel 2for easier start of the winding process and a lowered position,represented on FIG. 3, for which the wrapper is moved away from themandrel 2 to enable the winding of the band and the formation of thespool 3. The latter increases in diameter with the winding process andas the line of contact 30 of the band M with the spool 3 moves awaytherefore from the winding axis 20 by following a curve 34 representedas a dotted line on FIG. 3.

[0072] As indicated, the deflecting member 5 must follow an increase indiameter of the spool while remaining in optimum position inside thedihedron G to enable the air trapped in the boundary layer to escape.

[0073] The deflecting member 5 must therefore follow a curve 34′analogue to the path 34 of the line of contact 30 by moving apart,however, slightly thereof to take into account the fact that thedihedron G closes gradually with the winding process.

[0074] Therefore the position of the deflecting member 5 relative to thediameter of the spool 3 may be determined by calculation or empirically.

[0075] To enable gradual displacement of the deflecting member 5, thelatter is installed at the end of a support 6 whereof the orientationand the length may vary relative to the diameter of the spool 3.

[0076] As shown on FIG. 3, the support 6 may be composed of two armspaced apart, arranged at both ends of the profile 5 constituting thedeflecting member and liable to rotate round a shaft 60, hinged at itsends, on both sides of the chassis 22 of the wrapper F.

[0077] Each arm 6 carries the body of a jack 61 whereof the stem 62 isfitted, at its end, with an attachment part 63 of the hollow profile 5.The latter is linked by a flexible hose at a fixed pipework on thesupporting arm 6 for the air sucked in to escape through the slots 55,55′.

[0078] The chassis 22 of the wrapper F carries on the other hand amember 7 for controlling the rotation of the support 6, composed of atleast one lever hinged round an axis 70 and carrying a toothed sector 71which engages a toothed pinion 64 rotatably interconnected with one ofboth arms which form the support 6 and are interconnected in rotation.The other branch of the lever 7 is hinged on the stem of a jack 72resting on the chassis 22 and which controls thus the rotation of thesupport 6 between a retracted position 6 a, and a position spaced apart6 b corresponding to the maximum diameter of the spool 3.

[0079] In the retracted position 6 a which is also represented on FIG.1, the profile 5 and both its supporting arms are folded in the jig ofthe chassis 22 of the wrapper F and do not disturb therefore thepositioning of the latter on the mandrel 2 for starting the windingprocess.

[0080] After winding into a sufficient number of spires to place theband M under the traction necessary to the rolling process, the controlmember 7 rotates both supporting arms 6 until a position 6 c for whichthe axis of the jack 61 is substantially tangent to the spool at thebeginning of the winding process and the stem of the jack is broughtforward in order to place the deflecting member in the requestedposition 5 c close to the inner face of the band 4. The rotary speed ofthe mandrel 2 is then increased up to the level corresponding to therolling process at high speed of the band 4.

[0081] Using easy-to-design hydraulic means, the jacks 72 controllingthe rotation of the arm 6 and 61 adjusting the radial position of thedeflecting member 5 are slaved to the variation in diameter of the spool3 in order to follow the curve 34′ while remaining at the distancerequested from the inner face 41 of the band 4 and as close as possibleto the line of contact 30.

[0082] To this effect, the jacks 61 and 72 are fitted with positionsensors and controlled by an appropriate circuit in order to adjust withaccuracy the position of the profile 5 relative to the diameter of thespool which is determined itself on the basis of the number of turns ofthe mandrel 2 while taking into account the thickness of the band 4.

[0083] The installation is fitted, to do so, with sensors and withcalculation means which may be programmed in order to determine theprofile of the curve 34′ followed by the deflecting member 5.

[0084] Obviously, it is also necessary to take into account the positionof the wrapping roll 16 which determines the angle of application of theband 4 on the spool 3 and the position of the line of contact 30.

[0085] When the diameter of the spool reaches its maximum value, the arm6 adopts the position 6 b, the stem 62 of the jack being retractedcompletely.

[0086] Upon completion of the winding process, the spool 3 is withdrawnand the rotary support 6 is folded in its position 6 a inside the jig ofthe wrapper F. The latter may then be raised to engage on the mandrel 2,in order to start the winding process of a new spool.

[0087] The invention which has just been described in the case of aspool winder may also be applied to a deflecting roll, for example, theroll intended for measuring the flatness 15. The band M is then appliedunder traction on an angular sector of the roll 15 and the deflectingmember 5 is placed, as previously, in the dihedron G between the band 4during the winding process and the portion of the surface of the roll 15placed upstream of the line of contact 30.

[0088] The deflecting roll 15 having constant diameter, the deflectingmember 5 remains in the same position with respect to the roll and maybe placed, for example, at the end of a fixed supporting arm.

[0089] As previously, the deflecting member 5 may be a hollow profileemerging into an exhaust conduit 53, toward the outside, of a portion ofthe air trapped in the boundary layer 43 in order to reduce the dynamicpressure at the end of the dihedron G, at the line of contact 30. Oneavoids thus the formation of an air cushion which, on the one hand,might cause lateral floating of the band on the deflecting roll and onthe other hand, in the case of a flatness roll, might disturb themeasurement.

[0090] The reference signs inserted after the technical characteristicsmentioned in the claims, solely aim at facilitating the understandingthereof and do not limit their extent whatsoever.

1. A method for stabilising high speed running of a band-type productalong a longitudinal direction, the band (4) being applied from a lineof contact (30), over at least one angular sector of rotary revolutionsurface (3) around an axis (20) crosswise to the running direction, andconnecting tangentially to the rotary surface (3) while forming, on theupstream side in the running direction, a dihedron (G) delineated, onone side by an outer face (31) of the rotary surface (3) and on theother side, by an inner face (41) of the band (4) along which a portionof the surrounding air forms a boundary layer (43) trapped with the band(4) toward the line of contact (30), a method wherein the conditions ofcirculation of the air in the upstream dihedron (G) are modified bymeans of a hollow deflecting member (5) having a first face (50)directed toward the inner face (41) of the band (4) and a second face(50′) directed toward the outer face (31) of the rotary surface (3),characterised in that the first face (50) of the deflecting member (5)is tilted toward the inner face (41) of the band (4), in the runningdirection thereof, in order to decrease gradually the passageway sectionof the air trapped with the band, along the inner face (41) thereof, bycausing an increase in the pressure of the air trapped in the convergent(C₁) thus formed, with respect to the pressure prevailing inside thehollow deflecting member (5) which communicates, on the one hand withthe convergent C, by at least one orifice (55) provided in said tiltedface (50) and, on the other hand, with the outside, the differentialpressure thus created determining the exhaust toward the outside of acertain air flow rate passing through said orifice (55) and theseparation of the remaining portion of the air mass constituting theboundary layer (43).
 2. A method for stabilising a band according toclaim 1, characterised in that, the second face (50′) of the deflectingmember (5) is tilted toward the rotary surface (3), in the rotarydirection thereof, in order to generate, by a converging effect, anincrease in pressure along said second face (50′) and the exhaust of aportion of the air trapped with the rotary surface (3), toward a lowerpressure zone, passing through at least one orifice (55′) provided insaid second face (50′).
 3. A device for stabilising high speed runningalong a longitudinal direction, of a band (4) being applied from a lineof contact (30), over at least one angular sector rotary revolutionsurface (3) around an axis (20) crosswise to the running direction, andconnecting tangentially to the rotary surface (3) while forming, on theupstream side in the running direction, a dihedron (G) delineated, onone side by an outer face (31) of the rotary surface (3) and on theother side, by an inner face (41) of the band (4) along which a portionof the surrounding air forms a boundary layer (43) trapped with the band(4) toward the line of contact (30), a deflecting member (5) beingplaced in the dihedron (G) in order to modify the conditions ofcirculation of the air trapped with the band (4), said deflecting member(5) having a first face (50) directed toward the inner face (41) of theband (4) and a second face (50′) directed toward the outer face (31) ofthe rotary surface (3), characterised in that, at least the first face(50) of the deflecting member (5) is tilted toward the inner face (41)of the band (4), in the running direction thereof and is fitted with atleast one orifice (55) emerging into an inner space (51) provided insidethe deflecting member (5) and connected to an outer zone, said tiltedface (50) forming, with the inner face (41) of the band (4), aconvergent (C₁) wherein the pressure increases with respect to thepressure in the inner space (51), the differential pressure determiningthe exhaust, through the orifice (55) and the inner space (51), of acertain amount of air and the separation of the remaining portion of theair mass trapped in the boundary layer (43).
 4. A device according toclaim 3, characterised in that the inner space (51) of the hollowdeflecting member (5) is connected to an outer zone (54) situatedoutside the upstream dihedron (G), at a pressure lower than the pressure(P) in the convergent (C₁) at the inlet orifice (55).
 5. A deviceaccording to claim 4, characterised in that the inner space (51) of thedeflecting member (5) is connected to an outer zone situated atatmospheric pressure.
 6. A device according to claim 3, characterised inthat the second face (50′) of the deflecting member (5), directed towardthe rotary surface (3), is tilted with respect thereto, in order to forma convergent determining an increase in pressure of the air trapped withthe rotary surface (3), whereof a portion is evacuated toward the outerzone (54) connected to the inner space (51) passing through at least oneorifice (55′) provided in said second face (50′).
 7. A stabilisationdevice according to any of the claims 3 to 6, characterised in that therevolution surface whereon is applied the band is a deflecting roll (D)with a cylindrical profile, determining a change in direction of therunning plane of the band (M).
 8. A stabilisation device according toany of the claims 3 to 6, characterised in that itsaid device isarranged upstream of a spool (3) for winding the band into superimposedspires, in order to prevent the trapping of air between the spires (31,32).
 9. A stabilisation device according to claim 8, characterised inthat the deflecting member (5) of the air consists of a hollow profile,installed on a supporting means (6) adjustable relative to the diameterof the spool (3), in order to maintain the deflecting member (5) inoptimum position with respect to the inner face (41) of the band (4), asthe latter is wound gradually into a spool.
 10. A device according toclaim 9, characterised in that the profiled deflecting member (5) of theair is installed at the end of at least one supporting arm (6) having avariable length and rotatably mounted around an axis (60) parallel tothe axis (20) of the spool (3), said arm (6) being associate with meansfor adjusting (7) its orientation and (61) its length, relative to thediameter of the spool (3), to position the profiled member (5) insidethe upstream dihedron (G).
 11. A device according to claim 10,characterised in that the supporting arm (6) is rotatably mounted aroundan axis parallel to the axis of the spool and carries a hydraulic jack(61) having a first element attached to the arm (6) and a second element(62) slidingly mounted on the first element and carrying the deflectingmember (5), the position of the second element (62) with respect to thefirst (61) being adjusted relative to the diameter of the spool (3). 12.A device according to claim 10 and 11, characterised in that the meansfor adjusting the orientation of the supporting arm comprises a lever(7) rotatably connected to the supporting arm (6) and whereof theangular position is adjusted by a hydraulic jack (72).
 13. A deviceaccording to claim 12, characterised in that the lever (7) is rotatablymounted around an axis (70) parallel to that (60) of the supporting arm(6) and is interconnected with a toothed sector (71) with a circularprofile centred round the axis (70) of the lever (7) of the crank andengaging a toothed wheel (64) rotatably interconnected with thesupporting arm (6).
 14. A device according to claim 9 to 13,characterised in that the supporting means (6) for adjusting thedeflecting member is installed on a wrapper (F) associated with thespool (3) for easier beginning of the winding thereof, the supportingmeans (6) being folded in the jig of the wrapper (F) when the latter isat the beginning of the winding position and unfolded after winding afew spires and spacing the wrapper apart (F), in order to place thedeflecting member (5) close to the band (M), in the upstream dihedron(G).
 15. A use of a stabilisation device according to any of the claims3 to 6, in a rolling mill for a metal band, the stabilisation device (5)being arranged upstream of at least one deflecting roll (D) placed onthe path of the band, in order to ensure direct application of the bandon the roll without interposition of an air layer capable of disturbingthe guiding of the band.
 16. A use of a stabilisation device accordingto claim 6 to 15, in a rolling mill for a metal band including at leastone rolling stand (10) associated with a roll (15) for measuring theflatness whereon the band is applied under traction, the stabilisationdevice (5) being arranged upstream of the flatness roll (15) in order toprevent the trapping, between the band (M) and the roll (15), of an airlayer capable of disturbing the flatness measurement.
 17. A use of astabilisation device according to claim 8 to 14, in a rolling mill for ametal band (M) including a winder (E) placed at the end of the line, thestabilisation device (5) being placed in the dihedron (G) upstream ofthe line of contact (30) with the band (4) already wound in order toprevent the trapping of air between the spires (31, 32) and to ensureguiding stability of the band (4) during the winding process.